Preheat oven to 350°.,Recipe uses a 9-inch pie pan.,In a bowl, combine beef, egg, bread crumbs, salt, herbs, mustard and garlic powder.,Pat evenly in pan.,Layer with potatoes, onion and mushrooms.,Reserve some mushrooms to garnish pie.,Cover with foil.,______,Remove foil, top with cheeses, sprinkle with parsley; arrange reserved mushroom slices around ring of pie.,Return to oven until cheese melts. Serves 6.